With few exceptions, barrier operator systems, such as those controlling upward acting sectional garage doors, so-called rollup doors, gates and other motor operated barriers, are remotely controlled devices. Typically, they are remotely controlled by one or more building mounted or hand held wireless remote control devices such as radio frequency (RF) code transmitters. These RF transmitters, upon actuation by the user, usually send access codes and commands, via packet data, to a radio frequency receiver associated with the barrier operator. A controller unit also associated with the barrier operator then receives and decodes the data from the RF receiver. Upon receiving and decoding the packet data, and verifying the access codes, the barrier operator then either opens, closes, or stops the barrier, depending upon the command.
More recently, the communication protocol between the remote RF transmitters and the RF receiver uses code-hopping encryption for the access codes, sometimes referred to as “rolling codes,” to prevent code interception and unauthorized actuation of the barrier operator. Accordingly, the rolling code is transmitted as part of the packet data along a single fixed RF “channel.” By “channel,” as used throughout the specification and claims, is meant the communication path between the RF transmitter and RF receiver along which the encoded primary RF signal travels. Each channel will accommodate inter alia a different main radio frequency signal along with any sidebands thereof.
The rolling or hopping code changes with each new transmission in accordance with a stored algorithm to prevent unauthorized capture of the codes, its security dependent upon the secrecy of the encryption algorithm and of the secret key. A plurality of remote RF transmitters can be used to send the required access code and data to a single RF receiver integrated into the barrier operator, but in each case the transmission from each transmitter proceeds along its own single fixed RF channel.
The packet style data sent by the RF transmitters to the RF receiver is typically 58 to 69 bits, and tens to hundreds of milliseconds, in length, and the packet as a whole is repeatedly transmitted for as long as the user actuates the transmitter. Because these RF transmissions are sent on a fixed, single RF channel, RF noise in the channel causes reduced reception range, and the transmitter must often be actuated, and the packet data repeatedly transmitted, for extended periods of time to ensure the data is received. If the channel has heavy interference, then reception is completely blocked and the wireless system breaks down as the code-hopping scheme cannot mitigate RF noise in the channel.
Therefore, there is a need for a better system of wireless code communication, preferably for code hopping transmissions, to improve reception, security, and operation of barrier operator systems, that does not incur the disadvantages associated with single channel RF transmission.